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<div class="titlepage"><div><div><h4 class="title">
<a name="fusion.iterator.concepts.bidirectional_iterator"></a><a class="link" href="bidirectional_iterator.html" title="Bidirectional Iterator">Bidirectional
        Iterator</a>
</h4></div></div></div>
<h6>
<a name="fusion.iterator.concepts.bidirectional_iterator.h0"></a>
          <span class="phrase"><a name="fusion.iterator.concepts.bidirectional_iterator.description"></a></span><a class="link" href="bidirectional_iterator.html#fusion.iterator.concepts.bidirectional_iterator.description">Description</a>
        </h6>
<p>
          A Bidirectional Iterator traverses a <a class="link" href="../../sequence.html" title="Sequence">Sequence</a>
          allowing movement in either direction one element at a time.
        </p>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl class="variablelist">
<dt><span class="term"><code class="computeroutput"><span class="identifier">i</span></code></span></dt>
<dd><p>
                A Bidirectional Iterator
              </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">I</span></code></span></dt>
<dd><p>
                A Bidirectional Iterator type
              </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">M</span></code></span></dt>
<dd><p>
                An <a href="http://www.boost.org/libs/mpl" target="_top">MPL</a> integral
                constant
              </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">N</span></code></span></dt>
<dd><p>
                An integral constant
              </p></dd>
</dl>
</div>
<h6>
<a name="fusion.iterator.concepts.bidirectional_iterator.h1"></a>
          <span class="phrase"><a name="fusion.iterator.concepts.bidirectional_iterator.refinement_of"></a></span><a class="link" href="bidirectional_iterator.html#fusion.iterator.concepts.bidirectional_iterator.refinement_of">Refinement
          of</a>
        </h6>
<p>
          <a class="link" href="forward_iterator.html" title="Forward Iterator">Forward Iterator</a>
        </p>
<h6>
<a name="fusion.iterator.concepts.bidirectional_iterator.h2"></a>
          <span class="phrase"><a name="fusion.iterator.concepts.bidirectional_iterator.expression_requirements"></a></span><a class="link" href="bidirectional_iterator.html#fusion.iterator.concepts.bidirectional_iterator.expression_requirements">Expression
          requirements</a>
        </h6>
<p>
          In addition to the requirements defined in <a class="link" href="forward_iterator.html" title="Forward Iterator">Forward
          Iterator</a>, the following expressions must be valid:
        </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Expression
                  </p>
                </th>
<th>
                  <p>
                    Return type
                  </p>
                </th>
<th>
                  <p>
                    Runtime Complexity
                  </p>
                </th>
</tr></thead>
<tbody>
<tr>
<td>
                  <p>
                    <code class="computeroutput"><a class="link" href="../functions/next.html" title="next"><code class="computeroutput"><span class="identifier">next</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
                  </p>
                </td>
<td>
                  <p>
                    <a class="link" href="bidirectional_iterator.html" title="Bidirectional Iterator">Bidirectional
                    Iterator</a>
                  </p>
                </td>
<td>
                  <p>
                    Constant
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    <code class="computeroutput"><a class="link" href="../functions/prior.html" title="prior"><code class="computeroutput"><span class="identifier">prior</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
                  </p>
                </td>
<td>
                  <p>
                    <a class="link" href="bidirectional_iterator.html" title="Bidirectional Iterator">Bidirectional
                    Iterator</a>
                  </p>
                </td>
<td>
                  <p>
                    Constant
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    <code class="computeroutput"><a class="link" href="../functions/advance_c.html" title="advance_c"><code class="computeroutput"><span class="identifier">advance_c</span></code></a><span class="special">&lt;</span><span class="identifier">N</span><span class="special">&gt;(</span><span class="identifier">i</span><span class="special">)</span></code>
                  </p>
                </td>
<td>
                  <p>
                    <a class="link" href="bidirectional_iterator.html" title="Bidirectional Iterator">Bidirectional
                    Iterator</a>
                  </p>
                </td>
<td>
                  <p>
                    Constant
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    <code class="computeroutput"><a class="link" href="../functions/advance.html" title="advance"><code class="computeroutput"><span class="identifier">advance</span></code></a><span class="special">&lt;</span><span class="identifier">M</span><span class="special">&gt;(</span><span class="identifier">i</span><span class="special">)</span></code>
                  </p>
                </td>
<td>
                  <p>
                    <a class="link" href="bidirectional_iterator.html" title="Bidirectional Iterator">Bidirectional
                    Iterator</a>
                  </p>
                </td>
<td>
                  <p>
                    Constant
                  </p>
                </td>
</tr>
</tbody>
</table></div>
<h6>
<a name="fusion.iterator.concepts.bidirectional_iterator.h3"></a>
          <span class="phrase"><a name="fusion.iterator.concepts.bidirectional_iterator.meta_expressions"></a></span><a class="link" href="bidirectional_iterator.html#fusion.iterator.concepts.bidirectional_iterator.meta_expressions">Meta
          Expressions</a>
        </h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Expression
                  </p>
                </th>
<th>
                  <p>
                    Compile Time Complexity
                  </p>
                </th>
</tr></thead>
<tbody><tr>
<td>
                  <p>
                    <code class="computeroutput"><a class="link" href="../metafunctions/prior.html" title="prior"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">prior</span></code></a><span class="special">&lt;</span><span class="identifier">I</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
                  </p>
                </td>
<td>
                  <p>
                    Amortized constant time
                  </p>
                </td>
</tr></tbody>
</table></div>
<h6>
<a name="fusion.iterator.concepts.bidirectional_iterator.h4"></a>
          <span class="phrase"><a name="fusion.iterator.concepts.bidirectional_iterator.expression_semantics"></a></span><a class="link" href="bidirectional_iterator.html#fusion.iterator.concepts.bidirectional_iterator.expression_semantics">Expression
          Semantics</a>
        </h6>
<p>
          The semantics of an expression are defined only where they differ from,
          or are not defined in <a class="link" href="forward_iterator.html" title="Forward Iterator">Forward
          Iterator</a>
        </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Expression
                  </p>
                </th>
<th>
                  <p>
                    Semantics
                  </p>
                </th>
</tr></thead>
<tbody><tr>
<td>
                  <p>
                    <code class="computeroutput"><a class="link" href="../functions/prior.html" title="prior"><code class="computeroutput"><span class="identifier">prior</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
                  </p>
                </td>
<td>
                  <p>
                    An iterator to the element preceding <code class="computeroutput"><span class="identifier">i</span></code>
                  </p>
                </td>
</tr></tbody>
</table></div>
<h6>
<a name="fusion.iterator.concepts.bidirectional_iterator.h5"></a>
          <span class="phrase"><a name="fusion.iterator.concepts.bidirectional_iterator.invariants"></a></span><a class="link" href="bidirectional_iterator.html#fusion.iterator.concepts.bidirectional_iterator.invariants">Invariants</a>
        </h6>
<p>
          In addition to the invariants of <a class="link" href="forward_iterator.html" title="Forward Iterator">Forward
          Iterator</a>, the following invariants always hold:
        </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
              <code class="computeroutput"><a class="link" href="../functions/prior.html" title="prior"><code class="computeroutput"><span class="identifier">prior</span></code></a><span class="special">(</span><a class="link" href="../functions/next.html" title="next"><code class="computeroutput"><span class="identifier">next</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">))</span> <span class="special">==</span> <span class="identifier">i</span> <span class="special">&amp;&amp;</span>
              <a class="link" href="../functions/prior.html" title="prior"><code class="computeroutput"><span class="identifier">prior</span></code></a><span class="special">(</span><a class="link" href="../functions/next.html" title="next"><code class="computeroutput"><span class="identifier">next</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">))</span> <span class="special">==</span> <a class="link" href="../functions/next.html" title="next"><code class="computeroutput"><span class="identifier">next</span></code></a><span class="special">(</span><a class="link" href="../functions/prior.html" title="prior"><code class="computeroutput"><span class="identifier">prior</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">))</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><a class="link" href="../functions/prior.html" title="prior"><code class="computeroutput"><span class="identifier">prior</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> <span class="special">==</span> <a class="link" href="../functions/advance_c.html" title="advance_c"><code class="computeroutput"><span class="identifier">advance_c</span></code></a><span class="special">&lt;-</span><span class="number">1</span><span class="special">&gt;(</span><span class="identifier">i</span><span class="special">)</span></code>
            </li>
<li class="listitem">
              Using <code class="computeroutput"><a class="link" href="../functions/prior.html" title="prior"><code class="computeroutput"><span class="identifier">prior</span></code></a></code> to traverse a
              sequence will never return a previously seen position
            </li>
</ul></div>
<h6>
<a name="fusion.iterator.concepts.bidirectional_iterator.h6"></a>
          <span class="phrase"><a name="fusion.iterator.concepts.bidirectional_iterator.models"></a></span><a class="link" href="bidirectional_iterator.html#fusion.iterator.concepts.bidirectional_iterator.models">Models</a>
        </h6>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
              <a class="link" href="../../adapted/std__pair.html" title="std::pair"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code></a>
              iterator
            </li>
<li class="listitem">
              <a class="link" href="../../adapted/boost__array.html" title="boost::array"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span></code></a>
              iterator
            </li>
<li class="listitem">
              <a class="link" href="../../container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a>
              iterator
            </li>
<li class="listitem">
              <a class="link" href="../../container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a>
              iterator
            </li>
<li class="listitem">
              <a class="link" href="../../view/single_view.html" title="single_view"><code class="computeroutput"><span class="identifier">single_view</span></code></a>
              iterator
            </li>
<li class="listitem">
              <a class="link" href="../../view/iterator_range.html" title="iterator_range"><code class="computeroutput"><span class="identifier">iterator_range</span></code></a>
              (where adapted sequence is a <a class="link" href="../../sequence/concepts/bidirectional_sequence.html" title="Bidirectional Sequence">Bidirectional
              Sequence</a>)
            </li>
<li class="listitem">
              <a class="link" href="../../view/transform_view.html" title="transform_view"><code class="computeroutput"><span class="identifier">transform_view</span></code></a>
              (where adapted sequence is a <a class="link" href="../../sequence/concepts/bidirectional_sequence.html" title="Bidirectional Sequence">Bidirectional
              Sequence</a>)
            </li>
<li class="listitem">
              <a class="link" href="../../view/reverse_view.html" title="reverse_view"><code class="computeroutput"><span class="identifier">reverse_view</span></code></a>
            </li>
</ul></div>
</div>
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<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman,
      Dan Marsden, Tobias Schwinger<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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